Blending agent for gasoline



Patented Dec. 26, 1939' Edwin R. Giililand,

Cambridge,

Mass., and

Baphael Rosen, Elizabeth, N. J., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application February 6, 1937,

Serial N0. 124,468

9 Claims. (01. 44-9) This inven ion relates to blending agents for gasoline to improve the anti-knock properties thereof and pertains more particularly to organic blending agents employed in relatively high con-.. centrations in the gasoline. I 1

The trend toward increasing the compression ratio of internal combustion motors in order to obtain greater eiflciency has naturally increased the demands for motor fuel having higher antiknock properties. The anti-knock properties of motor fuels is usually expressed in octane number, obtained by the method recommended by the Cooperative Fuel Research Committee of the Society of Automotive Engineers.- According to this method an increase inoctane number indigates an increase in anti-knock properties of the ue Motor fuels produced by the common methods of refining do not have suiiiciently high octane number to meet the requirements'for high compression motors employed for aviation andautomobiles. To meet this deficiency, it is a common practice to add an anti-knock agent such as tetraethyl lead or other metallo-organic com-. pounds. The extent of improvement obtained by the addition of 1 cc. tetraethyl lead to gasoline is known as the lead susceptibility of the gasoline and varies with different types of gasoline.

Straight run gasoline of the same octane number derived from the various crude petroleum sources and cracked gasoline from-different types of cracking processes have diilerent lead sus-.

. ceptibilities. The reason why a measured quantity of tetraethyllead does not have the" same effect on all types of gasoline having the same octane number has not been definitely established. It hasbeen found that as a general rule, subject to some exceptions, the higher the octane number of the gasoline the poorer the lead susceptibility. For this reason the octane number of high grade gasoline cannot be boosted to the same extent by. the addition of 1 cc. of tetraethyl lead as can be obtained when added to a low grade gasoline. Moreover, a gasoline which has been improved by the addition of 1 cc. of tetraethyl lead is not improved to -the same extent by the addition of a second cc. In other words, the improvement in octane number obtained by tetraethyl lead is not a linear'function of its concentration. For these reasons'the octane improvement which can be obtained by the addition of tetraethyl lead to the highest grade gasoline' without -forming objectionable lead deposits in the motor and introducing other operating difliculties, is limited. Moreover, in some inhibitors; Furthermore, in order to impart localities the use of tetraethyl lead or other lead alkyls is prohibited and in other localitiesrestrictions are placed upon the concentration of lead.

Partly with the view of removing these limita- 6 tions and partly to produce cheaper substitutes for tetraethyl lead and other metallo-organic compounds, intensive investigations have been made to discover other anti-knock blending agents which may be used in lieu of, or'in addi- 1. tion to tetraethyl lead and other lead alkyl compounds.

More particularly, there is an urgent need for cheap blending agents which will impart an improvement in octane number which may be used 1 in much greater concentrations than is desirable or permissible with respect to tetraethyl lead. I

From previous investigations, it has been found that certain of the oxygenated hydrocarbons such as alcohols, ethers, ketones and aldehydes and particularly those having branched molecular structure improve the octane number when blended with gasoline. These compounds arenot as potent as lead alkyls'and are used in concentrations of entirely different order than when using leaded alkyl compounds. Whereas these organic blending agents are used in concentrations ranging from 10 to 50 or more percent, for

example, tetraethyl leadis used in concentrations from .05 to .5 percent. In view of the necessity of using such large concentrations of anti knock blending agents of this type, these agents must not only be capable of effecting a material imnot materially lower than that of gasoline, and must not affect the functioning of other gasoline addition agents such as anti-oxidants and gum maximum benefits to multi-cylinder motors, it is desirable to have the anti-knock agent vaporize with the constituents of the gasoline which have the lowest anti-knock properties. It is now known that because of ;fractional separation in the intake manifold of the motor each cylinder in a multi-cylinder motor does not obtain the same proportion of all constituents of the gasoline under all conditions of operation. For example, some cylinders may be charged with a fuel which is relatively rich in higher boiling constituents and lean in lower boiling constituents. Other cylinders may be charged with fuel rich in intermediate constituents and boiling constituents. In order to prevent knocking in such motors the charge to each cylinder should have high anti-knock properties.

It isgenerally known that the lower boiling fractions of gasoline have better anti-knock properties than the intermediate and higher boiling fractions. Consequently, for most effective results the anti-knock agent should vaporize with the intermediate and higher boiling fractions of the gasoline. Since tetraethyl lead vaporizes with the highest boiling fraction, it is mwt effective in reducing knock in the cylinders pulling a charge rich in high-boiling and normally low anti-knock constituents and it is least effective for reducing knock in the cylinderspulling a charge rich in intermediate or low-boiling constituents. Since the low-boiling constituents have relatively high anti-knock, it is particularly desirable that the anti-knock agent vaporize with the intermediate fractions of the gasoline. In addition to all these requirements for a satisfactory blending agent of this type, such agents must be available in large quantities at relatively low cost somewhat comparable to gasoline.

Moreover, to meet requirementsfor extremely :righ octane number motor fuel for some types of aviation service metallo-organic anti-knock agents have been added to the blend in order to get a further improvement in octane number. In other cases it isdesirable to use lower concentrations of such blending agents and to supplement their use with tetraethyl lead because of the failure of such agents to satisfactorily meet all of the above requirements. In either case, it is important that the blended fuel have a good lead susceptibility. As already pointed out, the lead susceptibility in general decreases as the octane number of base fuel increases and this generality, subject to some exce'ptions, applies to blended fuels as well as to unblended gasoline.

It has been found, however, that some blending agents are not only capable of imparting an improvement in octane number, but the lead susceptibility of the resulting blend is much greater than would reasonably be expected from the octane number of the blend. Blending agents of this character are of great value since they make possible the production of motor fuel having an octane value materially higher than could be obtained otherwise.

Our invention has for its object to provide a blending agent which will satisfactorily meet th requirements above set forth.

More specific objects of our invention are to provide organic blending agents which are more potent for improving the octane number of the gasoline and which when blended with'gasoline will produce a blended motor fuel which has an extremely high lead susceptibility, much greater than would be expected from the octane number As a result of our investigations we have discovered that ethers boiling within the range of gasoline or not materially higher, which have a branched chain structure, and which are formed. from diand tri-hydric alcohols are more potent in improving octane number, and produce a blend of better lead susceptibility than any of the straight chain compounds thus far investigated. We have also found that those having a branched chain containing a tertiary carbon atom are most effective. These compounds may be classified as glycol or glycerol ethers.

The glycol. ethers may be expressed by the.

general formula R1O-R20R3, where R: is an alkylene radical having at least 2 carbon atoms, R1 is an alkyl radical, R3 is either hydrogen or an alkyl radical and R1, R2 or R: is a branched group, preferably one having a tertiary or quaternary carbon atom. A tertiary carbon atom is one which is directly connected to three separate alkyl radicals and a quaternary carbon atom is one which is directly connected to four separate alkyl radicals.

The glycerol ethers may be expressed by th general formula:

where R: is an alkyl radical having at least 3 carbon atoms, R1 and R3 are the. same as the first formula and R4 is either hydrogen or an alkyl radical.

The ethers of these classes which boil within,

or not materially above the end point of the gasoline, are the only ones adapted for use as anti-knock blending agents. Among the ethers thus far investigated, the monoand di-tertiary ether of ethylene glycol have been found most effective. The octane number and lead susceptibility of the mono-tertiary butyl ether is shown in the following table: I

A blend containing 10% of the di-tertiary butyl ether of ethylene glycol was found to increase the octane number of 73.9 to 77.3 and to have a clear blending value of 114.

It will be noted that the addition of 25% monotertiary butyl ether of ethylene glycol improved the octane number 12.9 points (from 73.9 to 86.8) and that this can be further increased 4.3 points (86.8 to 91.1) by the addition of 1 cc. of tetraethyl lead. This shows exceptionally good lead susceptibility considering the extremely high octane number of the blend.

It will also be noted from the blending values given in the table, that it is possible to produce a fuel having an octane number in excess of 100 by either of these compounds;

Tests made on these same general class of compounds, but which do not have a branched chain structure have shown them to be definitely pro-- knock. The data obtained from these tests are shown in the following table:

It will beapparent from these data that the addition of these unbranched compounds as distinguished from the branched compounds herein described actually induce knocking in the motor fuel:

Among other branched ethers of ethylene glycol which are particularly effective as anti-knock agents are the monoand di-isopropyl ether, isopropyl tertiary butyl ether, methyl tertiary butyl ether, ethyl tertiary butyl, the branched monoand di-amyl ethers, methyl, ethyl, propyl and isopropyl branched amyl ethers and the various branched butyl-amyl ethers. The corresponding ethers of propylene glycol and butylene glycol having boiling points within the desired range are likewise effective.

Among the effective glycerol ethers are the 1,2 .di-methyl, tri-methyl, tri-ethyl and the 1,3

di-isopropyl.

These ethers may be readily prepared by refluxing the glycols or the glycerlnes with branched alcohols in the presence of a catalyst such as sulfuric acid. For example, monoand ditertiary butyl ether of ethylene glycol may be preparedby refluxing tertiary butyl alcohol with ethylene glycol in the presence of sulfuric acid.-

As a specific example, 800 cc. oftertiary butyl alcohol, 200 cc, of ethylene glycol and 36 cc. of 66 B. sulfuric acid were refluxed for one hour .at 70 C. The mixture was then neutralized and fractionated giving 175 cc. of mono-tertiary butyl of ethylene glycol, 50 cc. of di-tertiary butyl ether of ethylene glycol and 75 cc. of unreacted glycol.

The blending agent may comprise any one of the branched ethers of diand tri-hydric alcohols boiling below or not materially above the end point of gasoline or it may comprise any desired mixture of these compounds.

Another advantage of using this type of ethers as blending agents for gasoline is that certain of them, such as monoand di-tertiary butylether of ethylene glycol boil in the intermediate range of gasoline and therefore are particularly effective for reducing knocking in cylinders fed with a charge rich in intermediate constituents. The mono-tertiary butyl ether boils at 302 F. and the di-tertiary at 336 F.

By the term ether", as used in this description and in the claims, is signified compounds containing true ether groups, characterized by carbon atoms interlinked through an oxygen atom, with only a. single oxygen atom joineddirectly to a carbon atom in an ether group.

Having described the preferred embodiment of our invention, it is understood that it embraces such other modifications andvariatioris as come within the spirit and scope thereof. It is also understood that it is not our intention to unnecessarily limit the invention or to dedicate any novelfeatures thereof.

We claim:

1. A motor fuel for internal combustion motors comprising gasoline hydrocarbons blended with a branched ether of a polyhydric alcohol selected from the class consisting of glycols and glycerols in substantial amount sufllcient to improve the anti-knock properties of the motor fuel, said ether boiling substantially within the gasoline boiling range and having only a single oxygen atom linked directly to a carbon atom in an ether group.

2. A motor fuel for internal combustion motors containing gasoline hydrocarbons and a tertiary ether of a polyhydric alcohol selected from the class consisting of glycols and glycerols, in a substantial portion sufllcient to materially improve the anti-knock properties of the fuel, said ether boiling substantially within the gasoline boiling range and having only a single oxygen atom joined directly to a carbon atom in an ether group.

3. A motor fuel for internal combustion motors comprising gasoline hydrocarbons blended. with asubstantial quantity of a branched ether of a glycol to materially improve the anti-knock properties of the motor fuel, said other boiling substantially within the gasoline boiling range and having only one oxygen atom linked directly to a carbon atom in an ether group.

4. A motor fuel for internal combustion in motors comprising gasoline hydrocarbons blended with a substantial amount of a tertiary ether of a glycol to materially improve the anti-knock properties of the motor fuel, said ether boiling substantially within the gasoline boiling range and having only a single oxygen atom attached directly to a carbon atom in an ether group.

5. A motor fuel for internal combustion motors comprising gasoline hydrocarbons blended with a substantial amount of a branched ether of a glycerol to materially improve the anti-knock properties of the motor fuel, said ether boiling substantially within the gasoline boiling. range and having only one oxygen atom linked directly to a carbon atom in an ether group.

6. A motor fuel for internal combustion motors comprising gasoline hydrocarbons blended with a substantial amount of a tertiary ether of a glycerol to materially.improve the anti-knock properties of the motor fuel, said ether boiling substantially within the gasoline boiling range and having only a single oxygen atom linked directly to a carbon atom in an ether linkage.

7. A motor fuel for internal combustion motors comprising gasoline hydrocarbons blended with a substantial quantity of a tertiary butyl ether of ethylene glycol to materially improve the antiknock properties of the motor fuel.

8.- A motor fuel for internal combustion motors comprising gasoline hydrocarbons blended with a substantial quantity of mono-tertiary butyl ether of ethylene glycol to materially improve vknock properties of the motor fuel.

EDWIN R. GILLILAND. RAPHAEL ROSEN. 

